PH345: Winter 2025
Is there a moment where a galloping horse has all hooves off the ground?
Eadweard Muybridge, 1878. Public Domain
Schematic representation of late-prophase chromosomes (1000-band stage) of man, chimpanzee, gorilla, and orangutan, arranged from left to right, respectively, to better visualize homology between the chromosomes of the great apes and the human complement.
Figure 2, Yunis and Prakash (1982)
[S]lice the data into parts according to one or more data dimensions, visualize each data slice separately, and then arrange the individual visualizations into a grid (Ch21, Wilke, 2019).
Called ‘small multiples’ (Tufte, 1991), ‘trellis plots’ (Becker et al., 1996), or ‘facet plots’ (Wickham, 2016).
Introduces a third dimension (first two dimensions being x and y). Essentially another aesthetic.
Tufte’s principles of graphical excellence:
Present many numbers in small space
Make large data sets coherent
Use when you want to focus audience attention on how differences
Faceting variable must be categorical
Each mini-plot should (normally) have same structure: common axes, scales, etc
New Zealand statistician, Chief Scientist at Posit PBC
Creator of ggplot2 and the tidyverse
John Chambers Award for Statistical Computing (2006); Fellow of ASA (2015); COPSS Presidents’ Award (2019)
ggplot2facet_wrap(): wrap a 1D ribbon of plots into 2D gridfacet_grid(): create a 2D grid of plotsSee Chapter 16 of ggplot2 book (https://ggplot2-book.org/facet)
facet_wrap()# Install and load datasauRus if not already installed
if(!require(datasauRus)) {install.packages("datasauRus");library(datasauRus)}
ggplot(datasaurus_dozen) +
geom_point(aes(x = x, y = y), size = 1) +
facet_wrap(vars(dataset), ncol = 5) +
guides(color = "none") +
theme(text = element_text(size = 20)) facet_grid() doesn’t work hereWrapped facet by US States, ordered by size of workforce. Easy to compare trends across states. Unemployment band provides anchors
Anna Maria Barry-Jester, https://fivethirtyeight.com/features/as-u-s-life-expectancies-climb-people-in-a-few-places-are-dying-younger/
Sort of a facet grid by categorized latitude and longtitude. The trend line provides an anchor. The amount of purple and orange allow to immediately determine
Becker, R.A., Cleveland, W.S. and Shyu, M.J., 1996. The visual design and control of trellis display. Journal of computational and Graphical Statistics, 5(2), pp.123-155.
Tufte, E.R., 1991. Envisioning information. Optometry and Vision Science, 68(4), pp.322-324.
Wickham H (2016). ggplot2: Elegant Graphics for Data Analysis. Springer-Verlag New York. ISBN 978-3-319-24277-4, https://ggplot2.tidyverse.org.
Wilke, C.O., 2019. Fundamentals of data visualization: a primer on making informative and compelling figures. O’Reilly Media.
Yunis, J.J. and Prakash, O., 1982. The origin of man: a chromosomal pictorial legacy. Science, 215(4539), pp.1525-1530.